Exchange Client - Message changes not syncing to server

Exchange Client - Message changes not syncing to server

I use Outlook on my iPad and Pixel Phone. On both devices, Zoho is configured as Exchange. Yet, messages I delete on one device are not actually deleted from the server. Exchange configuration should mean that I’m always looking at, and working in, the master copy of the mail database. No matter which copy of Outlook I open, I should see the same set of messages. Any idea which this isn’t working properly? Thanks!